*{
    margin: 0;
    padding: 0;
}
body{
    padding: 20px;
}
.box{
    position: relative;
    width: 800px;
    height: 600px;
    border: 1px solid red;
    .menu{
        position: absolute;
        left: 0;
        top: 0;
        width: 150px;
        height: 200px;
        background-color: #00aeec;
    }
}